So I have these brown spots all over my brussell sprouts leaves? I thought maybe it was because it was so dry? Anyone familiar with this? I haven't grown them before so I'm a little unfamiliar with them.

Those are lambs quarters/ pigweed/ goosefoot/ amaranth (all common names for the same weed) in your picture. It is a delicious spring green that often shows up in new gardens and areas the soil has been disturbed. The spots on the leaves look like insect damage to me . Brussels Sprouts appear the same as cabbage , broccoli and related brassicas in seedlings and early growth.

Don't weed them and toss them if you like spinach .. Young lambs quarters ( nicest name for them) make a great green like spinach.. Just clean them , trim off root and steam or boil just to wilted .. You can serve with a squeeze of lemon , vinegar , bit of butter or plain.... just as you would spinach or a similar green. Those "weeds" are great eating .